Some features of the desktop portal are currently not expected to work correctly for an unconfined (non-sandboxed) application. To build the GTK 4 test as a Flatpak app, use commands similar to these: flatpak --user remote-add --if-not-exists \ flathub https://flathub.org/repo/flathub.flatpakrepo flatpak --user install flathub org.gnome.Platform//41 flatpak --user install flathub org.gnome.Sdk//41 apt-get source libportal cd libportal-* flatpak-builder \ --force-clean --ccache --repo=_build/repo --install --user \ _build/app-Gtk4 build-aux/org.gnome.PortalTest.Gtk4.json